JPS5848019B2 - Spray cooling method and device for steel plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applied to steel sheet manufacturing equipment in a steel mill. The present invention relates to a method and apparatus for cooling a high-temperature steel plate on a conveyance path.

Generally related to cooling high temperature steel plates. Cooling, or normalizing, as a steel plate heat treatment is aimed at improving the strength and toughness of the steel plate by making the steel plate uniform and refining the structure to reduce variations in mechanical properties within the steel plate. Also, cooling is carried out after hot rolling. After hot rolling, the steel plate is passed through a leveler to bring it to a uniform temperature so that flatness can be straightened. The purpose of this process is to perform one process to prevent the formation of quenched structures in the steel plate after rolling, so that the next process can be carried out effectively and productivity can be increased.

When normalizing the steel plate mentioned above. That is. When a steel plate is heated to the austenitizing temperature and then cooled, it would be possible to forcibly change the cooling rate within a range that does not cause quench hardening. In other words, if the heated steel plate is cooled at a cooling rate equal to one steel plate material. The rear cooling table can be made space-shaped, and the high-temperature steel plate is not placed on the table for a long period of time, improving safety.

Cooling for further normalizing. In any case of cooling after rolling, deformation of the steel sheet during cooling is very problematic.

Conventional. How to cool a heated steel plate. Natural cooling method. Forced air cooling method. Injection water cooling method has been adopted, and recently air cooling method has been adopted. Spray cooling methods have been considered in which water is sprayed using an atomizing agent such as steam.

The outline will be explained below.

(a) Natural cooling method: Leave the steel plate on a cooling table or tape step. This is a natural air cooling method. Maximum heat transfer coefficient is 80 kca
l,/m'・Hr・℃, and the cooling rate is very slow. Cooling stand. As a cooling table, a vast area is required, and the metal structure cannot be refined.

(Note) Forced air cooling method A method in which a large amount of air is blown onto the surface of a steel plate using a blower or the like. Even in this case, the heat transfer coefficient between the steel plate and the air is estimated to be approximately 100 kcal/m'・Hr・℃ {ζ, and it is difficult to increase the heat transfer coefficient beyond that value. It still has the disadvantages of the natural cooling method described above.

(/→ Injection water cooling method This is a method in which water is injected from a metal tube with porous holes.This method is conventionally used for quench hardening and cooling.

However, with this method, the water is not atomized, but becomes water droplets or water streams that are drawn across the steel plate. Even if the amount of water was reduced, it was extremely difficult to maintain a heat transfer coefficient between the steel plate and the jetted water of less than 1000 kcal-Hr·°C.

Additionally, there was a drawback that the areas where the water droplets hit were quenched and hardened.

Furthermore, this method is conventionally used for hardening. 500 to 5000 l/m'-mi per steel plate surface area
The amount of water used was large, and it was difficult to control the amount of water to a small amount of 100 e/m2·min or less.

(d) A spray cooling method in which water is sprayed using an atomizing agent such as air or steam.

This method was recently devised. Although it has the advantage of being able to vary the cooling rate over a wide range. There is a disadvantage that a large amount of atomizing agent and atomizing energy are required to atomize water.

That is, when air is used as an atomizing agent, 1. Usually 1
1 300-400 e of air is required to atomize 1 e of water.

This means that the compressor power required to pressurize 300e of air by 6kiffl is 2500W, as the energy required to atomize 14 tons of water per minute. In the method of the present invention, which will be described later, when the nozzle water pressure is 10 kg/i, the power required for the pressurizing pump is 50 W, whereas 50 times the power is required.

Also, because the atomizing agent passes through the nozzle at high speed. 90-110
There is a problem in that it generates a large noise of dB(A).

Furthermore, the cooling method using cooling water described above has the following problems.

During the transportation of steel plates through the steel plate production line and in each processing process. The steel plate is transferred using a horizontally installed table or the like.

Therefore, the steel plate cooling device also has a structure in which the steel plate is cooled by being installed horizontally, and the steel plate is cooled by cooling water sprayed from the top and bottom directions.

In this case, the way the cooling water escapes after hitting the steel plate is not the same on both the top and bottom surfaces of the steel plate. There is no problem with the bottom side of the steel plate, as the water remaining after cooling naturally falls off. Water remaining after cooling may accumulate on the upper surface of the steel plate.

If water accumulates on the top surface of the steel plate, effective cooling cannot be achieved through the residual water, and the water does not collect evenly on the top surface of the steel plate, resulting in uneven cooling. Therefore, the upper and lower surfaces cannot be cooled uniformly, and the Even the surface cannot be cooled uniformly.

Also, when water cooling a high temperature steel plate of 100℃ or higher. A film of steam is always generated between the cooling water and the steel plate.

What is the phenomenon of vapor film that occurs on the top and bottom sides of the steel plate? The difference is due to the above-mentioned reason that the way the cooling water escapes is different on the upper and lower surfaces. Furthermore, even on the same side, the phenomenon and characteristics of vapor film generation change depending on the temperature range of the steel plate. Heat transfer is reduced accordingly.

Therefore. A steel plate during water cooling experiences uneven cooling and changes in the heat transfer coefficient on each surface (thus causing deformation). When the steel plate is deformed, the way the residual water escapes from the top side of the steel plate changes, resulting in an even more uneven accumulation of water. As cooling conditions change even on the same surface, the steel plate becomes increasingly deformed, making uniform cooling impossible, and at the same time, the structure of the steel plate becomes non-uniform, making it extremely difficult to produce high-quality steel plates.

However, in the above method, deformation of the steel plate due to cooling water is not controlled at all. The deformation that has occurred has been corrected using a leveler or the like.

The present invention relates to cooling of a steel plate by spray cooling, which eliminates all of the above-mentioned problems, and is concerned with the speed of movement of the steel plate and the amount of sprayed ice. Water pressure supplied to the nozzle. Atomization method. A method and apparatus for cooling a steel plate, which uniformly cools the steel plate at a desired heat transfer coefficient without deforming the steel plate by appropriately changing the spray angle.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 and 2 show an example of an apparatus according to the present invention, in which multiple pairs of upper and lower disc rolls 1 are arranged at appropriate intervals. The roll 1 with the disk. The roll 1 is driven by the roll forward/reverse device 3 and is driven in the forward and reverse directions by the drive device 2. The steel plate 4, which is continuously carried in from the direction of the arrow in FIG. 1, can be reciprocated by the disc-equipped roll 1 after being carried in.

Among the rolls 1 with discs, the one above the upper roll with discs is. An elevating frame 5 of a required length is positioned facing the moving direction I of the steel plate 4 and is supported so as to be able to rise and fall from the elevating device 6l. A plurality of spray pipes 8 each having a plurality of spray nozzles 7 are attached in a direction perpendicular to the longitudinal direction of the lifting frame 5 as shown.
Furthermore, on the upper side of the elevating frame 5. Headers 9, 10 divided into at least two (two in this embodiment) are installed in the longitudinal direction of the lifting frame 5, and the headers 9, 10 are connected to the spray pipe 8I, and each header is connected to the spray pipe 8I. Telescopic tube 11. It communicates with the water supply device 13 via the water volume adjustment valve 12. By the operation of the lifting device 6, the spray nozzle T and the spray pipe 8 are raised and lowered together with the lifting frame 5, and the distance between them and the steel plate 4 can be adjusted freely. In addition, after the cooling water pressurized by the water supply device 13 is adjusted in water amount by the water amount adjustment valve 12, it is transferred to the hesodor 9,1.
0. It is sent to the spray nozzle 7 through the spray pipe 8. Here, water pressure can be used to atomize and spray. Further, below the roll with a disc on the lower side of the roll with a disc 1. Spray pipe 8. Spray nozzle l. Divided header-9', 10
"The said spray pipe 8. Spray nozzle γ, header
The headers 9 and 10 are arranged symmetrically with each other, and each header 9 and 10 is connected to a water supply device 13 via a water volume adjustment valve 12. After the amount of cooling water pressurized by the water supply device 13 is adjusted by the water amount adjustment valve 12, the header = 9', 10'. , spray pipe 8
and is sent to the spray nozzle γ. Here, water pressure is used to atomize and spray. Furthermore, the upper and lower headers - 9, 10, 9
', 10' {corresponding spray pipes. The spray nozzles are organized into upper and lower groups by each water volume adjustment valve 12, and are further divided into at least two or more groups in the longitudinal direction, with the inlet side (right side in Figure 1) being smaller. Edited by. The sequel was called Inu-hen.

or. As shown in FIG. 1, each of the water volume regulating valves 12 is individually controlled by the water volume control device 141 at 5 e/711'. - m
The flow rate is controlled to an arbitrary flow rate of i n to 50e/rrl·min.

Furthermore, the water flow control device 14 sets the upper limit of the water flow to 501/@”・m.
In or less. It also has the function of limiting the lower limit to 5e/m2·min or more.

Next, the spray nozzle γ and the spray nozzle attachment mechanism 1 will be explained with reference to FIGS. 3 to 5.

The spray nozzle γ used in this embodiment produces a spray effect by dividing the cooling water into water streams having two different vectors and then recombining them near the spray D of the nozzle.

For example, as shown in FIG. 3, a water conduit 18 passing through the center of the nozzle case 16 and a flow divider 19 having spiral guide vanes 1γ on the outer peripheral surface are installed.

At the nozzle γ, water entering from the inlet 15 exerts spray energy. The water going to the water conduit 18 is swirled by the guide vane 1γ and separated into vortices, which are then combined at the spray nozzle 19 and atomized by mutual interference of vectors and water pressure.

The bent pipe 20 equipped with such a nozzle γ at the tip is a rotary pipe joint 2.
It is connected to the spray pipe 8 via the pipe 1 and is rotatably supported in the width direction of the steel plate.

still. Instead of this rotary pipe joint 21, a flexible joint such as a rubber hose may be provided.

A support bar 22 is attached to the frame 5 so as to be located below the spray pipe 8 and parallel to the spray pipe. A touch roll guide 23 is provided corresponding to each individual nozzle γ. Attach the lower end of the guide 23 to the lower end of the cut roll 2.
The vertically movable slider 25, which is pivotally connected to the slider 4, is fitted into the vertically movable slider 25.

The slider 25 and the bent pipe 20 are connected by a link mechanism 26 that converts the vertical movement of the slider 25 into rotational movement of the nozzle γ.

In this embodiment, a rotary plate 2γ is fixed to the horizontal straight pipe portion of the bent pipe 20. The rotating plate 2γ and the slider 25 are connected by a link member 28. The rotation range of nozzle γ is from 0 to the vertical line.
The angle shall be 70°.

If the link member 28 is separated and joined with a sleeve nut, the length of the link member can be changed and the initial angle of the nozzle 7 relative to the plate can be adjusted.

Because of the above structure. The heated steel plate 4. It is carried in from the entrance side as shown by the arrow by a rotating roll with a disc 1. After being carried into this device as shown in the figure. The steel plate 4 is reciprocated by a forward and reverse rotation device 3.

After the cooling water is pressurized by the water supply device 13, the water volume adjustment valve 12
The water volume is adjusted with . Each header - 9, 10, 9', 1
The spray pipe 81 is led through the 0'. It is further atomized by a spray nozzle γ.

This atomized water is sprayed onto the upper and lower surfaces of the reciprocating steel plate 4. Steel plate 4 is cooled.

At this time, in cooling the above steel plate. This is because the steel plate 4 is made to reciprocate between the rolls 1 with discs. Spray nozzle γ
It is possible to correct the uneven cooling caused by the unevenness of small sprays between each other, that is, to uniformly cool the steel plate and prevent the steel plate from deforming during cooling. Furthermore, the load applied to the disc-equipped roll 1 is made uniform, and deformation of the disc-equipped roll can also be prevented.

Furthermore, if the nozzle γ is tilted in a certain direction in advance, the sprayed ice that is sprayed from the nozzle γ and hits the steel plate 4 will be. The horizontal force generated by the angle of inclination acts to push the residual water on the upper surface of the steel sheet one step in the width direction of the steel sheet.

As a result, the spray ice sprayed from nozzle 1. At the same time as cooling the steel plate 4, the residual water on the upper surface of the steel plate can be pushed out to remove residual water. Prevents uneven cooling due to residual water. That is, deformation of the steel plate 4 is prevented.

As mentioned above, the present invention is configured to prevent deformation of the steel plate 4 as much as possible. As a corrective measure when deformation occurs, there is the aforementioned rotation mechanism for the nozzle 4.

That is. If cooling is performed while holding the touch roll 24 at an appropriate position above the steel plate 4. If the steel plate 4 deforms (warps) beyond a certain level during cooling. Slider 25 is lifted. Link member 28. The nozzle γ is rotated via the rotating plate 21.

Therefore, the direction of the cooling water spray from nozzle γ changes. The sprayed ice does not accumulate on the upper surface of the IJ portion of the steel plate, but is blown away from the steel plate by the spray water pressure, thereby preventing uneven cooling due to residual spray ice. Improves the flatness of steel plates.

or. The cooling characteristics of the steel plate can be changed during cooling by using nozzles that are divided into two or more groups.
This makes it possible to obtain the cooling characteristics required from the viewpoint of the steel sheet material.

In other words, the amount of sprayed ice on the inlet side group is large.
By reducing the amount of sprayed ice for the Inukenkai group, it is possible to increase the initial cooling rate and slow down the cooling rate from the middle.

One more. The thickness of the steel plate 4 carried between the disk-attached rolls 1 in this apparatus changes as appropriate, but in this case, the distance between the nozzle γ and the steel plate 4 is adjusted by the lifting device 6.

This makes it possible to obtain uniform cooling even if the thickness of the steel plate changes, and to make the spraying conditions on the upper and lower surfaces of the steel plate 4 uniform.

The steel plate after cooling. The roll 1 with discs is switched to normal rotation drive and carried out.

Next, the cooling effect and the like in the present invention will be explained using specific numerical values.

In the present invention. The amount of sprayed ice per unit surface area of the steel plate 4 is 5 while reciprocating the steel plate 4 so that the product υt of the table speed υ-m/min and the plate thickness t is 20 to 150 m/min.
~50 e/rrl-min of water is atomized with a pressure of only 0.5 to 20 kii in the nozzle 7 and sprayed onto the surface of the steel plate. This method performs arbitrary cooling within the range of the above amount of sprayed ice without quenching and hardening the steel plate.

In the above specific example, the reciprocating motion of the steel plate 4 is between 20 and 150 m/m.
mln was selected because table speed and plate thickness are correlated with each other in terms of cooling uniformity. If the thickness of the board is small, it is better to move it faster. This is because it was found that the deformation is the smallest when the value of υt is 20 to 150 m/min. The amount of sprayed ice is 5 to 50e/m・m above.
The reason why it is set as in is that below 5e/m・min, the cooling rate becomes slow and rapid cooling cannot be expected compared to the conventional forced air cooling method mentioned above, and above 501/rn′・min, hardening occurs. Find out what to put away. The amount of sprayed ice that can be sprayed onto the steel plate surface to cool the steel plate 2 without quench hardening (normalizing) and to increase the cooling rate is 5 to 5 as described above.
0 e/rr? ．． This is because it was found that a value within the range of min is necessary.

or. In the present invention, the water pressure at the nozzle 7 is set to 0.5 to 20
The reason for choosing kl- is as follows.

That is. The amount of sprayed ice per unit surface area of the steel plate 4 is 5 to 50 with respect to the water pressure of the nozzle 7, which allows the inventor to obtain good atomization.
Experiments were conducted with different spray hole diameters within the range of g/m/min. When spraying with only water under pressure (the size of spray ice particles suitable for cooling steel plates is 700 μm)
The following is appropriate, so atomization of 700 μm or less is considered good), the minimum water pressure of the nozzle 7 needs to be 0.5 ky/i or more, and if it is less than this, the spray will be disordered, and the maximum water pressure is 20 ky/i or more.
kg/i or less and 50 l/ra: ・It is capable of spraying min water in a good atomized state, and 20 kii
Even if water is sprayed at a water pressure of 50 (!/m'min) at a water pressure of This is because only power consumption increases.

Furthermore, the reason why the nozzle inclination angle is set to 0 to 70 degrees is because if it is 70 degrees or more, the sprayed ice hardly hits the steel plate.

Next, the cooling effect in the above specific example will be described.

A steel plate heated to an austenitizing temperature was reciprocated using the apparatus of the above embodiment. When cooled by spraying on the upper and lower surfaces of the steel, the heat transfer coefficient at which the steel plate can be cooled at a cooling rate that does not cause quench hardening is 100 to 800.
kcal/m''·Hr'C. It was found that the steel plate could be cooled at a high cooling rate.

The heat transfer coefficient of this 100 to 800 kcal/m
n, spray water amount 5~50e/min 1 nozzle water pressure can be changed arbitrarily by 1 for cooling within the range of 0.5~20ky/i. As a result, the steel plate could be cooled uniformly at any cooling rate without quench hardening.

In addition, the amount of sprayed ice (g/m・min) and the heat transfer coefficient α (k c
a l /8Hr·°C) is as shown in FIG.

A in Figure 6 is the local and overall heat transfer coefficient when water is atomized. This is the heat transfer coefficient that allows a steel plate to be cooled at a cooling rate that does not cause quench hardening when water is atomized and cooled at an amount of sprayed ice of 5 to 50 e/m'min.

or. B shows the local heat transfer coefficient on the steel plate surface when water is injected without atomization. As can be seen from the above, it has become clear that the cooling effect of the present invention described above cannot be achieved with water cooling for rice promotion in which water is injected without being atomized.

Next is the conventional natural cooling method. In the present invention, the amount of sprayed water is 50
1/m・min, 5 e/m2・min and plate thickness 3
The cooling rate at the center of the plate thickness was investigated by cooling the steel plate of 5 parts. As shown in FIG. 1, the results showed that the amount of atomized water varied.

In Figure 5, ■ indicates cooling with spray water at 5 e/m'min, and ■ indicates cooling with spray water at 50 e/rrbmin. (2) was cooled using the conventional natural cooling method.

As is clear from these, when cooling a steel plate from 850℃ to 300℃. Conventional cooling method ■ takes 2000 seconds. In the cooling method I of the present invention, the time is 1000 seconds. In addition, in the present invention (2), 200 seconds is sufficient.

From this, a steel plate with a length of Low and a thickness of 35 mm is
When cooling 10 sheets in 0 seconds. In contrast to ■, the length of the cooling table is required to be 100m. In case (2), a total table length of 20 m is sufficient, including 10 m for the implementation equipment and 10 m for the table to transfer the steel plate to remove it with a crane. Therefore, according to the present invention, the length of the cooling table can be reduced to 1/5 compared to the conventional cooling method.

As described above, according to method 1 of the present invention, (1) Standard plate thickness is 35mm. A heated steel plate. Temperature range 850
By adjusting the amount of water in the range of 5 to 50 e/m2・W per unit area of the upper and lower surfaces of the steel plate between ℃ and 300℃, the heat transfer coefficient can be increased to 100 to 800 kca1/m2・H.
Since cooling can be performed at any cooling rate within r.degree. C., normalizing cooling can be performed that suits the steel sheet material.

([1) Compared to the conventional natural cooling method due to the above l. Because it can cool down at a sufficiently fast rate. (iii) The length of the cooling table on which the steel plate is placed can be reduced.
Water with a water pressure of 0.5 to 2.0 k7 per unit surface of a steel plate at a nozzle of 5 to 5012/711 min is divided into two water streams with different vectors at the nozzle. Furthermore, by merging the water particles, the water particles are atomized to a size of 700μ or less and sprayed onto the upper and lower surfaces of the steel plate, so the steel plate can be uniformly cooled without locally quenching and hardening. By doing so, the amount of water within the above range. Any heat transfer coefficient within the range of 100 to 800 kcal/m2・Hr・℃ can be obtained just by changing the water pressure. Furthermore, the amount of water used is smaller than the conventional spray water cooling method. (IV) Since water is atomized using only water pressure and no atomizing agent is used, no power is required and the noise level is significantly lower than that using an atomizing agent. According to the device of the present invention, it becomes even lower. (V) One spray nozzle in the longitudinal direction is divided into two or more groups. The cooling characteristics of the steel plate can be changed during cooling. (VD) By using rolls with discs, the contact area between the steel plate and the roll can be reduced, and uneven cooling due to the rolls can be prevented. (vii) The spray nozzle can be raised and lowered. Therefore, even if the thickness of the steel plate changes significantly, the spray conditions on the surface of the steel plate can be made uniform. Φ111) The direction of the nozzle's cooling water spray changes to follow the warpage of the steel plate. The sprayed ice is blown away from the top of the steel plate by the spray water pressure without any accumulation on the top surface of the warped part of the steel plate. Prevents uneven cooling due to residual spray water. The flatness of steel can be improved. (1x) The metal structure of the steel plate can be made finer by 1, which improves the strength and toughness. A steel plate with at least sufficient strength can be produced by adding an amount of alloy.

Also, the fact that the carbon equivalent can be reduced by reducing the amount of alloy added can improve weldability. It can produce excellent effects such as

[Brief explanation of the drawing]

Fig. 1 is a side view showing an example of the device of the present invention, and Fig. 2 is a front view thereof. Figure 3 is a cross-sectional view of the spray nozzle, and Figure 4 is a front view of the spray nozzle mounting mechanism. Figure 5 A is a detailed diagram of the nozzle mounting mechanism. Figure 5 Mountain A Side view of Figure 5 A. Figure 6 shows the relationship between the amount of sprayed ice and the heat transfer coefficient. Fig. γ is a diagram showing the cooling rate at the center of the thickness of a plate having a thickness of 35 mm. 1 is a roll with a disc. 4 is a steel plate. 6 is a lifting device. γ is a spray nozzle, 12 is a water volume adjustment valve, and 14 is a water volume control device. 24
indicates a touch roll, and 26 indicates a link mechanism.

Claims (1)

[Claims] 1. In a method of cooling a heated steel plate with spray ice. The product of the moving speed of the steel plate in the longitudinal direction and the thickness of the steel plate is 2
0~15 0wn. While moving back and forth so that the distance is m/min. 5 to 50 per unit area of the upper and lower surfaces of the steel plate
e/rrl・m'+n. Water pressure 0.5-20kg/Cil
Supply cooling water to the nozzle. The nozzle separates the water into two streams with different vectors, which are then re-merged to form water droplets of 700 μm or less using only the energy of the cooling water, and are sprayed onto the steel plate. Based on the deformation of the steel that occurs during cooling, the spray direction of cooling water is automatically changed at an angle of 0 to 70' with respect to the vertical line, and the temperature range from 850°C to 300°C is maintained while preventing deformation of the heated steel plate. 100-800Kcal/77I2 by adjusting the amount of water in the range of 5-50e/m・min in between.
- A method for spray cooling a steel plate, characterized by uniform cooling at an arbitrary heat transfer coefficient within Hr°C. 2 Multiple pairs of upper and lower disc-equipped rolls that transport heated steel plates.
A drive device capable of rotating the disc-equipped roll in two directions, forward and reverse. A built-in flow divider is installed above and below the steel plate placed on the disc-equipped roll and separates the water into two water streams having different vectors so that the water can be sprayed using only water pressure energy, and the separated water streams are merged. Multiple pairs of upper and lower spray nozzles are configured to spray the spray. A steel plate displacement transmission device that allows the upper spray nozzles to rotate freely in the width direction of the steel plate and transmits the displacement of the steel plate to the spray nozzles to change the spray angle; and a device that raises and lowers the upper spray nozzles. A spray cooling device for a steel plate, characterized in that the spray nozzle is divided into upper and lower groups, and a water amount adjusting device for dividing the spray nozzles into at least two or more groups in the longitudinal direction and individually adjusting the water amount for each group.